New Alloy Could Make Solar Cheaper & More Efficient

Researchers from the University of Michigan have developed a new semiconducting alloy that could mean a huge leap forward for next generation solar cells. The cells dubbed concentrator photovoltaics can absorb light at the near-infrared spectrum which until now have been very costly to produce.

The researchers claim that the new formulation is easier to manufacture, compatible with current gallium arsenide semiconductors and reduces costs by over 25%. Previous generation concentrator photovoltaics gather and focus sunlight onto high-efficiency solar cells made of gallium arsenide or germanium.

The new generation panels are on track to achieve efficiency rates of over 50%, while conventional silicon solar cells max out at around 25%. “Flat-panel silicon is basically maxed out in terms of efficiency,” said Rachel Goldman, professor of materials science and engineering, and physics, whose lab developed the alloy. “The cost of silicon isn’t going down and efficiency isn’t going up. Concentrator photovoltaics could power the next generation.”

Current concentrator photovoltaics panels consist of 3 layers of semiconductor alloys sandwiched together. Each layer traps a different section of the light spectrum, allowing the rest to fall past and be trapped by the next layer. The near-infrared part of the spectrum has never been captured until now.

It has been a tough road to travel for the researchers as the alloy must be cheap enough, stable, durable and capable of absorbing infrared light. Goldman’s team came up with a new approach for keeping track of the many variables in the process. They combined measurement methods including X-ray diffraction and ion beam analysis with custom-built computer modelling.

The Growth Chamber

Using this new method, they found that a slightly different type of arsenic molecule would pair more effectively with bismuth. They tweaked the amount of nitrogen and bismuth in the mix, enabling them to eliminate an extra manufacturing step. They also found precisely the right temperature that enables the elements to mix smoothly and adhere to the substrate securely.

“‘Magic’ is not a word we use often as materials scientists, but that’s what it felt like when we finally got it right.” – Goldman

This new alloy could make the semiconductors used in concentrator photovoltaics as much as 30% percent cheaper to manufacture. This costs reduction is a giant step forward in making these high-efficiency cells practical for large-scale commercial electricity generation.

“Essentially, this enables us to make these semiconductors with fewer atomic spray cans, and each can is significantly less expensive,” Goldman said. “In the manufacturing world, that kind of simplification is very significant. These new alloys are also more stable, which gives makers more flexibility as the semiconductors move through the manufacturing process.”

Source: University of Michigan

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